Reversible pH-responsive supramolecular aggregates from viologen based amphiphiles - a molecular design perspective.

pH responsive self-assembled supramolecular systems in water hold tremendous promise spanning across the various realms of science and technology. Herein, we report the design and synthesis of benzyl viologen (BV) based amphiphiles and their ability to form pH responsive aggregates with a water soluble anionic dye (electron donor), a polyelectrolyte (PE), and a surfactant. To counter the low solubility of viologen derivatives, β-cyclodextrin (β-CD) was employed as a solubility promoter and the host-guest complexes were characterized by NMR spectroscopy.

Molecular Insights into Antioxidant Efficiency of Melanin: A Sustainable Antioxidant for Natural Rubber Formulations.

-(1,3-Dimethyl butyl)-'-phenyl--phenylenediamine (6-PPD) is a worldwide antioxidant commonly added to delay the thermo-oxidative degradation of tire rubbers. Unfortunately, 6PPD and its transformation product 6PPD-quinone are toxic to aquatic organisms (e.g.

Reciprocity of CO⋯π interactions with the dominant anion-π on fullerene (C)- amine-based organocatalysts: a mechanistic elucidation for addition decarboxylation reaction.

Reiterating the counterintuitive anion-π interactions that J. López-Andarias and coworkers [, 2017, , 13296-13299] have experimentally discussed in their pioneering work, the current investigation explores the role of such interactions in the fullerene-amine conjugate-based organocatalysis reaction density functional theory (DFT) protocols where the underlying catalytic reaction paths have been ascribed to unique transition state geometries. The reaction between MAHT (malonic acid half thioester) and nitrostyrene was reported to follow the addition and decarboxylation pathways.

Phosphonium Ionic Liquid-Activated Sulfur Vulcanization: A Way Forward to Reduce Zinc Oxide Levels in Industrial Rubber Formulations.

Extensive use of zinc oxide and accelerators such as diphenyl guanidine (DPG) in the vulcanization of rubber composites entail potential environmental risks. These are pervasive contaminants of roadway runoff originating from tire wear particles (TWPs). Herein, the effect of phosphonium ionic liquids (PILs) in styrene-butadiene rubber compounds was demonstrated with reduced ZnO loading and no DPG to minimize the environmental footprint of the vulcanization process.

Through-Bond-Driven Through-Space Interactions in a Fullerene C Noncovalent Dyad: An Unusual Strong Binding between Spherical and Planar π Electron Clouds and Culmination of Dyadic Fractals.

Hydrogen-bond-induced π-depletion as a criterion for π-stacking, a configurationally unique noncovalent strategy enabled an unconventional strong binding between the spherical -fulleropyrrolidine (NFP) and the planar distributions of π electron clouds of three substituted pybates to form noncovalent fulleropyrrolidino-4-(pyrenyl) butanoate dyads of large computed interaction energies, varying between 37.49 and 44.93 kcal/mol.

Synergistic effect of hydrophobic and hydrogen bonding interaction-driven viologen-pyranine charge-transfer aggregates: adenosine monophosphate recognition.

Understanding the role of non-covalent interactions that dictate and fine-tune the direction of self-assembly of functional molecules is crucial for developing stimuli responsive materials. Herein, we systematically designed and synthesized viologen derivatives with hydrophobic dodecyl chains and alkyl carboxylic acid functionalities. The complementary electronic and electrostatic counterpart of viologens was chosen as pyranine.

Design Principles of Interfacial Dynamic Bonds in Self-Healing Materials: What are the Parameters?

Polymers and polymer nanocomposites (PNCs) are extensively used in daily life. However, the growing requirement of advanced PNCs laid persistent environmental issues due to deformation-induced damage that once formed, does not vanish at future stages. Therefore, self-healing materials with significantly enhanced long life and safety have been designed to epitomize the forefront of recent advances in materials chemistry and engineering.

Role of Interface Structure and Chain Dynamics on the Diverging Glass Transition Behavior of SSBR-SiO-PIL Elastomers.

Intermolecular interactions between the constituents of a polymer nanocomposite at the polymer-particle interface strongly affect the segmental mobility of polymer chains, correlated with their glass transition behavior, and are responsible for the improved dynamical viscoelastic properties. In this work, we emphasized on the evolution of characteristic interfaces and their dynamics in silica (SiO NP)-reinforced, solution-polymerized, styrene butadiene rubber (SSBR) composites, whose relative prevalence varied with the phosphonium ionic liquid (PIL) volume fraction, used as an interfacial modifier. The molecular origins of such interfaces were examined through systematic dielectric spectroscopy, molecular dynamics (MD) simulations, and dynamic-mechanical analyses.

Oxidation State-Dependent Electronic Properties of Sulfur-Containing Thermally Activated Delayed Fluorescence Molecules.

Comparative studies of a series of sulfur-containing thermally activated delayed fluorescence (TADF) molecules and their oxidized compounds are carried out by means of electronic structure calculations. Aiming at investigating the effects of oxidation of bridged sulfur on the modulation of electronic structures of sulfur-containing TADF molecules, their geometrical structures, singlet (S) and triple (T) energies and their gap (Δ), the transition dipole moment, the spin-orbit coupling (SOC) between S and T states, the ionization potentials, and electron affinities are analyzed in detail to determine the structure-property relationships in these investigated TADF molecules and their corresponding oxidized counterparts. The electronic structure calculations show that the oxidation of bridged sulfur into the corresponding sulfoxide and sulfone significantly changes the electronic properties of TADF molecules.

Design of Dual Hybrid Network Natural Rubber-SiO Elastomers with Tailored Mechanical and Self-Healing Properties.

The preparation of natural rubber (NR)-silica (SiO) elastomeric composites with excellent mechanical properties along with better self-healing ability remains a key challenge. Inspired by the energy dissipation and repairability of sacrificial bonds in biomaterials, a strategy for combining covalent and noncovalent sacrificial networks is engineered to construct a dual hybrid network. Here, the approach used to fabricate the composites was self-assembly of NR, bearing proteins and phospholipids on its outer bioshell, with SiO via metal-ion-mediated heteroaggregation effected by reversible electrostatic and H-bonds.

Natural rubber-SiO nanohybrids: interface structures and dynamics.

Homogeneous dispersion of silica nanoparticles (SiO NPs) in natural rubber (NR) is a key challenge for engineering high-performance nanocomposites and elucidation of their structure on a molecular basis. Towards this, the present work devised a novel route for obtaining 3D self-assembled SiO NP-NR nanocomposites under aqueous conditions and in the presence of Mg, by establishing a molecular bridge that clamped the negatively charged NR and SiO colloidal particles with a favoured NR-SiO NP hetero-aggregation. The characteristic NR-SiO NP hetero-aggregates displayed a decreased heat capacity with increase in the SiO mass-fraction, implying a restricted NR chain mobility.

Carbon Nanosheets by Morphology-Retained Carbonization of Two-Dimensional Assembled Anisotropic Carbon Nanorings.

Two-dimensional (2D) carbon nanomaterials possessing promising physical and chemical properties find applications in high-performance energy storage devices and catalysts. However, large-scale fabrication of 2D carbon nanostructures is based on a few specific carbon templates or precursors and poses a formidable challenge. Now a new bottom-up method for carbon nanosheet fabrication using a newly designed anisotropic carbon nanoring molecule, CPPhen, is presented.

Structure and dynamics of a dl-homocysteine functionalized fullerene-C-gold nanocomposite: a femtomolar l-histidine sensor.

A functionalized fullerene-C-thiol mediated gold nanocomposite was realized using dl-homocysteine as a bifunctional ligand. The nanocomposite was designed by following electronic structure calculations via the DFT formalism. The computed electrostatic potential profile and the electronic HOMO-LUMO energy gap implied enhanced electron transport across the nanocomposite skeleton.

Structure and Dynamics of a N-Methylfulleropyrrolidine-Mediated Gold Nanocomposite: A Spectroscopic Ruler.

A mechanistic understanding of the structure and dynamics of a chemically tunable N-methylfulleropyrrolidine (8-NMFP)-assisted gold nanocomposite and its aggregation via a controllable interparticle interaction is reported as a function of the molar ratio and pH of the medium. Electronic structure calculations adopting density functional theory methods implied electrostatic interactions to play a dominant role between 8-NMFP and citrate-capped gold nanoparticles. MM molecular mechanics force field computations revealed intermolecular gold-gold interactions, contributing toward the formation of spherical composite aggregates.

Unusual Nonemissive Behavior of Rubrene J-Aggregates: A Rare Violation.

Structure-property correlations in rubrene (RB) colloidal J-aggregates were unravelled by steady state and time-resolved spectroscopy in conjunction with excited state density functional calculations. The RB J-aggregate with a slippage angle θ = 30.4°, estimated from the monomeric transition dipole moment directions, exhibited a broad fwhm of 1073 cm and a 5 nm red-shifted absorption band carrying a transition dipole moment (M⃗ = 1.

Regio-selective lipase catalyzed hydrolysis of oxanorbornane-based sugar-like amphiphiles at air-water interface: A polarized FT-IRRAS study.

Interfacial hydrolysis of oxanorbornane-based amphiphile (Triol C16) by Candida rugosa lipase was investigated using real-time polarized Fourier transform-infrared reflection absorption spectroscopy (FT-IRRAS). The kinetics of hydrolysis was studied by analyzing the ester carbonyl ν(CO) stretching vibration band across the two dimensional (2D) array of molecules at the confined interface. In particular, we demonstrate Triol C16 to form Michaelis-Menten type complex, like that of lipid-substrate analogues, where the Triol C16 head group remained accessible to the catalytic triad of the lipase.

A New Class of Nitroanilinic Dimer, the PNA O-Dimer: Electronic Structure and Emission Characteristics of O-Dimeric Aggregates.

p-Nitroaniline (PNA) has been reported as a "J" aggregate species. In retrospect, this communication confirms a radically different "oblique" orientation of the PNA units in all three solid, liquid, and gas phases of the dimer, the O-dimer. The nonvanishing transition dipole moments (TDM) associated with the allowed electronic excitations of the O-dimer, computed using electron-hole pair density distribution (EDD and HDD) analyses ascertained the two monomers to be inclined at slippage (θ) and polarization (α) angles of 18.

Structure and dynamics of H2O vis-á-vis phenylalanine recognition at a DPPC lipid membrane via interfacial H-bond types: insights from polarized FT-IRRAS and ADMP simulations.

Preferential and enantioselective interactions of L-/D-Phenylalanine (L-Phe and D-Phe) and butoxycarbonyl-protected L-/D-Phenylalanine (LPA and DPA) as guest with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (L-DPPC) as host were tapped by using real time Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). Polarization-modulated FT-IRRAS of DPPC monolayers above the phenylalanine modified subphases depicted fine structure/conformation differences under considerations of controlled 2D surface pressure. Selective molecular recognition of D-enantiomer over L-enantiomer driven by the DPPC head group via H-bonding and electrostatic interactions was evident spectroscopically.

Tailoring recognition clefts from non-specific recognition matrices in mixed molecular arrays.

Multi-component organic interfaces with molecular-level mixing were prepared by integrating benzoic acid appended thiophene amphiphile [4-(6-(thiophene-3-carbonyloxy)hexyloxy)benzoic acid] (T6BA) and (±)-α-lipoic acid onto the Au surface. On a flat surface with infinite radii of curvature, T6BA and (±)-α-lipoic acid, endowed with chemically distinct end-groups, provided sufficient length mismatch to gain conformational entropy leading to stripe-like patterns when the immiscible ligands co-adsorbed. Good quality multi-component organic interfaces and molecular islands could be fabricated via composition variation of the participating ligands.

Establishing the ellipsoidal geometry of a benzoic acid-based amphiphile via dimer switching: insights from intramolecular rotation and facial H-bond torsion.

Soft molecular ellipsoids conceived from 3,4-di(dodecyloxy)benzoic acid (DDBA) amphiphile draw attention to monomer structure design, intramolecular -COOH headgroup twist (ϕ°) and cyclic-acyclic dimer switching through facial H-bond torsion (ψ°). Generically, precipitation in hydrogen bonded systems has been the prime phenomenon once the critical aggregation concentrations were reached in the bulk solution. DDBA was no exception to this generalization.

L-tryptophan-induced electron transport across supported lipid bilayers: an alkyl-chain tilt-angle, and bilayer-symmetry dependence.

Molecular orientation-dependent electron transport across supported 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayers (SLBs) on semiconducting indium tin oxide (ITO) is reported with an aim towards potential nanobiotechnological applications. A bifunctional strategy is adopted to form symmetric and asymmetric bilayers of DPPC that interact with L-tryptophan, and are analyzed by surface manometry and atomic force microscopy. Polarization-dependent real-time Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS) analysis of these SLBs reveals electrostatic, hydrogen-bonding, and cation-π interactions between the polar head groups of the lipid and the indole side chains.

Interfacial Janus gold nanoclusters as excellent phase- and orientation-specific dopamine sensors.

This investigation, following our recent report on the one-pot hemi-micellar interfacial synthesis of Janus gold nanoclusters and the inter-cluster electron coupling establishing insulator-metal transition in the oriented Janus monolayers [Langmuir, 2010, 26(17), 14047], was to fabricate modified electrodes for sensing dopamine, the neurotransmitter. With a detection limit in the sub-nanomolar range, the apparent electron transfer rate constants for dopamine detection signified an intricate Janus cluster 2D phase dependency. Surface pressure as a thermodynamic variable controlled the electronic communication between the clusters as a result of varied inter-cluster distance and size, ultimately reflecting on the sensitivity and detection limit for dopamine sensing.

Novel two-component gels of cetylpyridinium chloride and the bola-amphiphile 6-amino caproic acid: phase evolution and mechanism of gel formation.

A two-component gel resulting from the amphiphilic cationic surfactant cetylpyridinium chloride (CPC) in the presence of a structure-forming bola-amphiphilic additive 6-aminocaproic acid (6-ACA) was realized and investigated. At a critical 6 wt % of 1:1 CPC:6-ACA, the yellow colored gel resulted from a 3:1 v/v CHCl(3):H(2)O critical binary solvent composition. The mixed amphiphilic system formed a 1:1 complex with a binding constant ~0.

Unraveling tryptophan modulated 2D DPPC lattices: an approach toward stimuli responsiveness of the pulmonary surfactant.

A molecular understanding on the preferential and selective interactions of L-tryptophan, a major component of surfactant proteins, with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) is important in the metabolic cycle of the pulmonary surfactant. In view of this, interfacial signals of interest in real time were tapped with aligned DPPC monolayers over a physiological tryptophan subphase using extremely surface sensitive 2D vibrational spectroscopy. Polarization-modulated and angle dependent Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS) of DPPC monolayers on water and L-tryptophan subphases depicted fine structure/conformation differences in the interaction modes, evidenced from changes in the vibrational band intensities and frequencies under conditions of controlled 2D surface pressure.

Tunable one-, two-, and three-dimensional self-assemblies from an acceptor-donor fullerene-N,N-dimethylaminoazobenzene dyad: interfacial geometry and temporal evolution.

Controllable fabrication of spontaneously ordered and varied geometry fullerene C(60) based molecular architecture was achieved upon hierarchical self-assembly of the fullerene-N,N-dimethylaminoazobenzene acceptor-donor hybrid (DPNME). Simple preparation techniques, such as Langmuir-Blodgett (LB), solution-cast, and immersion at the liquid-air and solid-air interfaces, were used without templates as a function of DPNME concentration, media pH, time, and supporting substrate characteristics. The resulting structures depending upon the preparation methods were investigated with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and molecular modeling, which revealed a delicate role of intermolecular donor-acceptor, π-π, and van der Waals interactions between the electron deficient fullerene core and the N,N-dimethylaminoazobenzene electron donor under neutral conditions.